Phone card

Phone card is one of the businesses in the USA. Foreign people use it a lot to communicate to their country, family, friends. It is much cheaper than the direct one, but it is often changing. As a foreing person, I use it to talk to my family, my friends in Madagascar, but I meet many problems using it.
First of all, when I use a phone card, I should know which one is much better to talk to. I mean I should know with wich phone card I can get much more minutes. Therefore I should ask someone from my country the better one to avoid an expense for nothing, because all phone cards are not necessary good for Madagascar.
Second problem is communicative problem. I have to make sure that the person to whom I want to talk to is turns on his phone and has time to talk, because when I do not reach him or her I loose my money. And when I reach him or her, I can not stop until the phone card is finished because if I stop talking and cut the communication, I loose at least 5mn.
Third problem is bad communication. Sometimes when I call to Madagascar, I can hear the person to whom I talk to but he or she do not hear me, so I have to stop even I loose money.
One month ago, I bought phone cards for $10 and kept them until I called, but after two days the company that made the phone card block the number, people could not use it at all. I thought that I lost my money again. I went to the seller to tell my problem using the phone card, he told that I could change them. I changed my phone cards just for saving money.
During this one month, I do not know which phone card may be good for calling to Madagascar. Today, one of my friends called me and said that there is a new one that is much better to call to Madagascar now. I went to the store but I did not find it yet. Hope that I can call soon.